Process and apparatus for the simultaneous production of acetylene and ethylene



Sept 7, 1965 H. ELSNER ETAL PROCESS AND APPARATUS FOR THE SIMULTANEOUS PRODUCTION OF ACETYLENE AND ETHYLENE Filed Deo. s. 1961 E DMZ-wr@ United States Patent O 3,205 048 PROCESS AND APPARATUS FOR THE SIMUL- TANEOUS PRODUCTON OF ACETYLENE AND ETHYLENE Horst Elsner, Spich, Heinz Diessel, Troisdorf, and Hans- Ewald Konermann, Siegburg, Germany, assignors to Dynamit Nobel Aktiengesellschaft, Troisdorf, Bezirk Cologne, Germany Filed Dec. 8, 1961, Ser. No. 157,999 Claims priority, application Germany, Dec. 22, 1960, D 35,004 2 Claims. (Cl. 23-277) This invention relates to a process and apparatus for the simultaneous manufacture of acetylene and ethylene.

Known processes for the manufacture of acetylene may be divided into two groups in accordance with the type of heat supply employed and, namely, into processes in which the heat supply is direct or indirect.

Included among the processes characterized by direct heating are the electric arc heating processes, the partial oxidation of hydrocarbons under utilization of special burner constructions, jet introduction of hydrocarbons into hot combustion gases, cracking of hydrocarbons utilizing moving heat carriers and the cracking of hydrocarbons by regenerative furnace heating.

The second group of ethylene and acetylene manufacturing processes which are characterized in that the heat required for the cracking of the hydrocarbons is supplied externally or indirectly are further subdivided according to the type of dilution agent utilized and, namely, into processes carried out under decreased pressure, processes carried out under addition of normally gaseous inert agents and processes carried out under addition of water vapor.

The processes directed to the use of an indirect heat supply and use of Water vapor as diluting agent and which are practised extensively and to which the instant invention is directed present numerous problems and disadvantages.

The formation of considerable amounts of carbon deposits in such processes results in decreased acetylene yields and, furthermore, gives rise to clogging and obstruction of the reaction tube. The deposition of carbon takes place in these processes as a result of the overheating of the tube walls occasioned because of the unfavorable ratios existing between the heating surface to the tube volume in tubes having large diameters.

Maintaining the reaction material for a minimum period of stay in order to obtain a specific reaction temperature similarly because of the unfavorable ratios of heating surface to tube volume becomes ever more diiiicult in the change-over to tubes of greater diameter as it is therein impossible to achieve short periods of stay at high reaction temperatures whereby improved acetylene yields are favored.

The above problems have required limiting the throughput capacity of the cracking tubes due to the technical and economical disadvantages resulting when tubes of increased diameter are utilized.

One of the objects of the invention is to provide a relatively simple and practical process for the production of ethylene and acetylene gas by conversion of hydrocarbons avoiding the aforesaid disadvantages.

Another object of the invention is the production of ethylene and acetylene by conversion of hydrocarbons which can be carried out economically.

Still another object is an apparatus for use in the production of ethylene and acetylene by conversion of hydrocarbons which is easily operated and adaptable to accurate temperature control.

3,265,348 Patented Sept. 7, 1965 Other objects and advantages will become apparent as the description proceeds.

The invention provides a new and different process of simultaneously producing acetylene and ethylene by conversion of normally fluid hydrocarbons by subjecting the said hydrocarbons to a cracking process at a high temperature in admixture with residual cracking gases, foreign gases or vapors, which comprises carrying out the cracking of the hydrocarbons to olen and thereafter to aceylene and ethylene, in one cracking zone which is subdivided into two sub-zones; the time of stay and temperature of the conversion gas in each of the said zones being determined by the profile thereof and specifically by the ratio of the heating surface to Volume ratio for one of said zones with respect tothe other; the ratio of the heating surface to volume of the second sub-zone being increased with respect to the same ratio prevailing in the irst said sub-zone; the heat required for heating the first or oleiin sub-zone being excess or waste heat produced in indirectly heating the second or acetylene and ethylene production sub-zone.

In the combination of tube sections differing in profile and in cross-section, there is achieved the favorable heating surface to tube volume ratios required to avoid the disadvantages heretofore associated with processes of the instant type. Furthermore, in accordance with the invention, due to the alterations in the profile, the rate of heat input to the conversion zone is no longer in direct proportion to, and in respect to, changes in the volume of the said zone. vention, the broadsides of the tube sections having alterations in proiile and in cross-section are directed toward the indirect heatsource, thus increasing the eiiciency and practicality of the invention. There is thus, in accordance with the invention, made possible by appropriate selection of variations in the proiile combinations of the conversion tube to adapt the iiow velocity of the reaction mixture as well as the ratio of heating surface to tube volume.

An additional advantage stemming from the teaching herein to employ reactor tubes of varying profile over that stemming from the use of the circular tubular reactors, the former permitting broadside heating, lies in the decrease in the temperature differentials existing between the tube Walls and the tube centers. Thereby the overheating of the tube Walls, particularly in the acetylene zone, with the formation of carbon deposits characteristic of the circular tubular reactors resulting in decreased yields of the desired cracking products is avoided. Furthermore, in the use of the non-circular, cracking tube profiles by an increase in the diameter of the profile part in contrast to the circular tube, the through-put per cracking tube may be essentially increased without any significant deterioration of the yield in acetylene.

In its simplest form, a cracking tube, in accordance with the invention, may be produced with non-circular profiling by treatment of a circular tube so as, by heat deformation, to press flat various sections thereof. l

As starting hydrocarbons for use in the production of ethylene and acetylene, in accordance with the invention there may be advantageously used benzine, propane, and butane. The conversion reaction is carried out at temperatures of within the range of 700 to 1000 C. for the olefin zone, and temperatures within the range of 900 to 1150 C. for the ethylene-acetylene zone.

In the conversion reaction the time of stay in the olein splitting zone amounts to between 0.04-05 second, whereas the time of stay in the ethylene-acetylene splitting zone amounts to between 0.0l-0.1 second.

Most advantageously, the dilution |ratios of the hydrocarbon to be converted:water vaporzinert gas fall within the following range 1:10-65: l-4.

Furthermore, in accordance with the in-v As illustrative of the manner in which the invention may be realized, reference is made to the drawings forming a part of this specification and in which drawings,

FIG. 1 is a vetrical section showing the general arrangement of apparatus in accordance with the invention;

FIG. 2 is a section taken along the line 2-2 of FIG. 1;

FIG. 3 is a section taken along the line 3--3 of FIG. 1; and

FIG. 4 is a further view of the apparatus shown in FIG. 1 taken on line 4-4 of FIG. 1 looking in the direction of the arrows.

Referring to FIGS. 1-4 of the drawing in detail, the tube 1 which extends through a furnace chamber 5 is divided into two cracking subzones, or chambers 2 and 3 which are inter-connected by the integrally formed tubular transition member 4. The first cracking chamber 2 is of substantially uniform circular cross section as shown by FIG. 2 and has an inlet extending beyond the furnace chamber 5 for the introduction of the hydrocarbon and diluting agent mixture. The second cracking chamber 3 is also of substantially uniform cross-section as shown by FIGS. 3 and 4, but diters from that of the rst chamber 2 in that it is a flattened oval, rather than circular, and has substantially parallel flattened broadsides 6 which are directed toward the source of heating provided in the facing furnace wall. The second cracking chamber 3 has an outlet extending beyond the furnace 5 for the removal of the ethylene and acetylene product.

The individual lengths and cross-sectional areas of the chambers 2 and 3 are selected so as to be inter-related with a length ratio ranging from 1:1 to 1:2 and an area ratio ranging from 1:1 to 3:1 as between Said chambers 2 and 3 respectively.

The ratio of the heating surface to volume of the first sub-zone to the ratio of the heating surface to the volume of the second sub-zone falls Within the range of 1:2 to 1:5. In the tube section 3 there are arranged a plurality of cross-pieces, or vanes 8 which extend transversely through said tube section 3 and project from the flattened broadsides 6 thereof. These vanes 8 connector join together the opposing broadsides 6, and thereby serve as supporting or reinforcing elements for maintaining the cracking tube profile, and simultaneously act as gas stream impingement or impact elements. As a result, there is produced a turbulence in the flowing gas stream which is very important in improving the heat exchange in the tube section 3.

The extraordinarily high conversions of the hydrocarbons, in accordance with the invention, are achieved by maintaining the hydrocarbon in the olen zone for a period which is respectively greater and at a temperature which is less than the period of stay and temperature of the subsequent ethylene and acetylene. It is in the latter zone that the oleiins formed are .further split to ethylene and acetylene and where the high temperatures and short exposure period are critical. Heretofore the achievement of the short exposure periods-ie., 10r1' to 102 seconds and temperatures of 1100 C.-was not satisfactorily obtainable. It is only through the combination of tube sections differing in profile and in cross-section, as taught herein, that the short periods of stay at the indicated high temperature as required for `the formation of ethylene and acetylene have been achieved.

The following examples are illustrative of the invention and are not to be construed to be a limitation thereof:

Example 1 The apparatus employed in the instant example of a process embodying the invention includes tube sections 2 and 3 dirnensioned as follows:

4 Volume cm.3 11,594 Outer diameter cm 8.9 Heating surface cm.2 6,291 Surfaceivolume cm.1 0.543 Cross sectionzinner dimensions cm.2 51.53 Tube section 3 acetylene zone (profile tube):

Heated length cm 225 Cross section:inner dimensions (192 x 12 mm.) cm.2 23 Volume cm.3 5,184 Perimeterzouter dimensions (200 x 20 mm.) cm 44.0 Heating surface cm.2 9,900 Surfacewolume cm.1 1.91 The operating conditions are as follows:

Maximum furnace temperature, C 1200 Maximum cracking temperature, C 1090 Benzine kg./h 7.84 Water vapor kg/h 50.68 Benzinenvater vapor kg./kg 16.46 Cracking gas ..Nm/h..- 10.54 Cracking gaszbenzine Nm.3/kg 1.3443 The final yield of ethylene and acetylene is as follows: Ethylene 10.0 vol. percent, 16.95 weight percent Acetylene 16.2 vol. percent, 25.50 weight percent Example 2 In the instant run in addition to the water vapor, residual cracking gas consisting essentially of water vapor and methane was charged into the cracking tube. The dilution amounted to per 1 kg. benzine vapor to 3.25 kg. Water vapor and 0.8 Nm.3 residual cleavage gas corresponding to a molar ratio of 1:15:3.

The apparatus as used in this run was composed of tube sections 2 and 3 as follows:

Tube section 2 olen zone (circular tube):

Heated length cm 225 Inner diameter cm 10 Volume ..cm.3 17,672 Outer diameter cm 11 Heating surface ..cm.2.. 7,776 Surface2volume cm.1 0.44 Cross section:inner dimensions cm.2 78.54 Tube section 3 acetylene zone (profile tube):

Heated length cm 225 Cross sectionzinner dimensions (196 x 18 mm.) cm.2 35.3 Volume cm.3 7,938 Perimeterzouter dimensions (206 x 28 mm.) cm 46.8 Heating surface cm.2 10,530 Surfacezvolume cm.-1 1.327 The operating conditions are as follows:

Maximum furnace temperature, C 1200 Maximum cracking temperature, C 1100 Benzine kg./h 20 Water vapor kg./h 65 Benzinezwater vapor Nm.3/h 16 Cracking gas Nm.3/h 35.3 Cracking gas:benzine -Nm.3/l g 1.765 The final yield of ethylene and acetylene is as follows: Ethylene 10.1 vol. percent, 22.48 weight percent Acetylene 10.3 vol. percent, 21.28 weight percent Example 3 Example 2 is repeated but the operating conditions were varied as follows:

Maximum furnace temperature, C 1180 Maximum cracking temperature, C 1080 Benzine kg./h 20 Water vapor kg/h-- 65 Benzinewater vapor ..-Nm3/h 16 Cracking gas Nm.3/h 34.8 Cracking gastbenzine Nm.3/kg 1.74

The final yield of ethylene and acetylene is as follows:

Ethylene 11.7 vol. percent, 25.67 weight percent Acetylene 9.0 vol. percent, 18.34 weight percent We claim:

1. An apparatus for simultaneously producing ethylene and acetylene by thermal cracking of a hydrocarbon, which comprises:

(a) a furnace chamber;

(b) a first tubular cracking chamber disposed within said furnace chamber so as to be heated thereby, said cracking chamber having an inlet end which eX- tends outside of said furnace chamber for the introduction of the hydrocarbon to be cracked, and an outlet;

(c) a second tubular cracking chamber disposed within Said furnace chamber so as to be heated thereby, said second cracking chamber having an outlet which extends outside of said furnace chamber for the removal of the ethylene and acetylene product, and an inlet, said second cracking chamber having a surface to volume ratio which is approximately 2 to 5 times that of the first cracking chamber;

(d) a plurality of vanes extending through said second cracking chamber and projecting from the eX- terior thereof; and,

(e) a tubular transition member which connects the outlet of said iirst cracking chamber to the inlet of said second cracking chamber, whereby when the furnace is heated, a hydrocarbon introduced into said first cracking chamber is heated therein and converted into an oleiin which passes through said transition member into said second cracking chamber where it is further heated, said vanes aiding the heating by inducing a turbulent flow of said olefin therein, with the ethylene and acetylene product being removed at the outlet of said second cracking charnber.

2. The apparatus of claim 1 wherein the first tubular cracking chamber is of substantially uniform circular cross-section, and the second tubular cracking chamber is of a substantially uniform flattened oval cross-section having a pair of substantially parallel flattened broadsides, and the transition member is integrally formed with said iirst and second cracking chambers, with the lengths of the portions of said cracking chambers within the furnace being such that the heating surface to volume ratio of said iirst and second cracking chambers is within the respective range of 1:2 to 1:5.

References Cited by the Examiner UNITED STATES PATENTS 1,777,782 10/30 Bundy 165--179 2,190,349 2/40 Beam 126-110 2,463,997 3/49 Rodgers 16S-179 2,679,544 5/54 Bills 260-679 2,786,877 3/57 King 260-683 2,816,942 12/ 57 Bills 260-679 FOREIGN PATENTS 17,584 7/00 Great Britain.

ALPHONSO D. SULLIVAN, Primary Examiner. 

